1 files changed, 51 insertions, 0 deletions
diff --git a/internal/id/ulid.go b/internal/id/ulid.go
new file mode 100644
index 000000000..b488ddfc4
--- /dev/null
+++ b/internal/id/ulid.go
@@ -0,0 +1,51 @@
+package id
+
+import (
+	"crypto/rand"
+	"math/big"
+	"time"
+
+	"github.com/oklog/ulid"
+)
+
+const randomRange = 631152381 // ~20 years in seconds
+
+// NewULID returns a new ULID string using the current time, or an error if something goes wrong.
+func NewULID() (string, error) {
+	newUlid, err := ulid.New(ulid.Timestamp(time.Now()), rand.Reader)
+	if err != nil {
+		return "", err
+	}
+	return newUlid.String(), nil
+}
+
+// NewULIDFromTime returns a new ULID string using the given time, or an error if something goes wrong.
+func NewULIDFromTime(t time.Time) (string, error) {
+	newUlid, err := ulid.New(ulid.Timestamp(t), rand.Reader)
+	if err != nil {
+		return "", err
+	}
+	return newUlid.String(), nil
+}
+
+// NewRandomULID returns a new ULID string using a random time in an ~80 year range around the current datetime, or an error if something goes wrong.
+func NewRandomULID() (string, error) {
+	b1, err := rand.Int(rand.Reader, big.NewInt(randomRange))
+	if err != nil {
+		return "", err
+	}
+	r1 := time.Duration(int(b1.Int64()))
+
+	b2, err := rand.Int(rand.Reader, big.NewInt(randomRange))
+	if err != nil {
+		return "", err
+	}
+	r2 := -time.Duration(int(b2.Int64()))
+
+	arbitraryTime := time.Now().Add(r1 * time.Second).Add(r2 * time.Second)
+	newUlid, err := ulid.New(ulid.Timestamp(arbitraryTime), rand.Reader)
+	if err != nil {
+		return "", err
+	}
+	return newUlid.String(), nil
+}